It has been proposed to use slot antennae for telecommunications.
A Vivaldi antenna is one example of slot antenna. In a Vivaldi antenna a slot may be terminated at one end by a circular cut-out in a conductor, this cut-out may have a diameter which is greater than the width of the slot. The slot is generally open at its other end, and may have a curved tapered profile so that it broadens out towards this open end, the width of this slot may be an exponential function of position along the length of the slot.